Article

Algal-derived organic matter as precursors of disinfection by-products and mutagens upon chlorination

Croucher Institute for Environmental Sciences and Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong, PR China.
Water Research (Impact Factor: 5.53). 01/2011; 45(3):1454-62. DOI: 10.1016/j.watres.2010.11.007
Source: PubMed

ABSTRACT

Algal-derived organic materials (including algal cells, hydrophilic and hydrophobic proteins) from Chlamydomonas sp. (a common green alga in local reservoirs), were chlorinated in the laboratory (20 °C, pH 7, Cl(2)/DOC ratio of 20 mg Cl(2) mg(-1)). Levels of disinfection by-products and mutagenicity (via Salmonella T100 mutation assay, -S9) over 2 h of chlorination time were determined. The hydrophilic proteins were more effective precursors of chloroform (35.9 μmol L(-1) at 120 min), 35 times greater than that from the hydrophobic proteins; whereas the hydrophobic proteins were more potent precursors of direct-acting mutagens (maximum level of 50.1 rev μL(-1) at 30 s) than the hydrophilic proteins (maximum level of 3.38 rev μL(-1) at 60 min). The mutagenicity of the chlorinated solutions generally reached a peak level shortly after chlorination and then declined afterwards, a pattern different from that of chloroform generation. The results indicate that algal hydrophilic proteins, containing low aromaticity and difficult to be removed via coagulation/flocculation, are important chloroform precursors. It is also suggested that hydrophobic organic intermediates with low molecular weight formed during chlorination may serve as the direct-acting mutagens.

0 Followers
 · 
21 Reads
  • Source
    • "Natural organic matter (NOM) which occurs in water reservoirs is mainly present in two forms: (i) allochthonous NOM of terrestrial origin dominated by humic substances (HS, mostly humic and fulvic acids) and (ii) autochthonous NOM, including mainly compounds derived from algae and cyanobacteria, i.e. algal organic matter (AOM). As well as HS, AOM has received increasing attention as it can cause either aesthetic concerns (i.e., colour, taste and odour) or undesirable health effects associated with disinfection by-products (DBPs) (Lui et al., 2011; Li et al., 2012), cyanobacterial toxins (Harada, 2004) and other toxic compounds contained in NOM (Ghernaut et al., 2011). Moreover, AOM may instigate serious problems in drinking water treatment processes, especially during the decline phase of an algal bloom, when high concentrations of cellular organic matter, consisting mainly of saccharide-like and protein-like substances, are released into the source water (Zhang et al., 2010; Nicolau et al., 2015). "
    [Show abstract] [Hide abstract]
    ABSTRACT: This study focuses on the effects of molecular interactions between two natural organic matter (NOM) fractions, peptides/proteins derived from cyanobacterium Microcystis aeruginosa (MA proteins) and peat humic substances (HS), on their removal by coagulation. Coagulation behaviour was studied by the jar tests with MA protein/HS mixtures and with single compounds (MA proteins or HS). Aluminium sulphate was used as a coagulant. Besides MA proteins, bovine serum albumin (BSA) was used as a model protein. For the MA protein/HS mixture, the removal rates were higher (80% versus 65%) and the dose of coagulant substantially lower (2.8 versus 5.5 mg L(-1) Al) than for coagulation of single HS, indicating the positive effect of protein-HS interactions on the coagulation process. The optimum coagulation pH was 5.2-6.7 for MA proteins and 5.5-6 for HS by alum. The optimum pH for the removal of MA protein/HS mixture ranged between pH 5.5-6.2, where the charge neutralization of negatively charged acidic functional groups of organic molecules by positively charged coagulant hydroxopolymers lead to coagulation. MA proteins interacted with HS, probably through hydrophobic, dipole-dipole and electrostatic interactions, even in the absence the coagulant. These interactions are likely to occur within a wide pH range, but they result in coagulation only at low pH values (pH < 4). At this pH, the negative charge of both MA proteins and HS was suppressed due to the protonation of acidic functional groups and thus the molecules could approach and combine forming aggregates. Virtually the same trends were observed in the experiments with HS and BSA, indicating that BSA is a suitable model for MA proteins under experimental conditions used in this study. The study showed that increases in organic content in source water due to the release of algae products may not necessarily entail deterioration of the coagulation process and a rise in coagulant demand.
    Full-text · Article · Jul 2015 · Water Research
  • Source
    • "It seems that DBP formation varies considerably with the genus and species of algae. As reported, the major source of the DBP precursors from algae is algal-derived organic matter (AOM), which is generally categorized into extracellular organic matter (EOM) and intracellular organic matter (IOM) (Fang et al., 2010b; Lui et al., 2011; Yang et al., 2011; Li et al., 2012; Wert and Rosario-Ortiz, 2013; Pivokonsky et al., 2014). The AOM in different algal cells contains different amounts of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) (Westerhoff and Mash, 2002; Nguyen et al., 2005; Lui et al., 2012), which can contribute to the source of precursor matter for carbonaceous DBPs (C-DBPs) and nitrogenous DBPs (N-DBPs). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Microcystis aeruginosa (blue-green alga) commonly blooms in summer and Cyclotella meneghiniana (diatom) outbreaks in fall in the reservoirs that serve as drinking water sources in Southeast China. Herein, an evaluation of disinfection by-product formation potential (DBPFP) from them during chlorination should be conducted. Five DBPs including trichloromethane (TCM), trichloronitromethane (TCNM), dichloroacetonitrile (DCAN), 1,1-dichloropropanone (1,1-DCP) and 1,1,1-trichloropropanone (1,1,1-TCP) were monitored. The formation potential of TCM and TCNM was enhanced with the increase of reaction time and chlorine dosage, whereas that of DCAN, 1,1-DCP and 1,1,1-TCP increased first and then fell with continuing reaction time. M. aeruginosa showed higher DBPFP than C. meneghiniana, the yield of DBPs varied with components of algal cells. The DBPFP order from components of M. aeruginosa was cell suspension (CS)≈intracellular organic matter (IOM)>extracellular organic matter (EOM)>cell debris (CD), which indicated that IOM was the main DBP precursors for M. aeruginosa. The yields of DBPs from components of C. meneghiniana were in the order of CS>IOM≈CD≈EOM, suggesting that three components made similar contributions to the total DBP formation. The amount of IOM with higher DBPFP leaked from both algae species increased with the chlorine dosage, indicating that chlorine dosage should be considered carefully in the treatment of eutrophic water for less destroying of the cell integrity. Though fluorescence substances contained in both algae species varied significantly, the soluble microbial products (SMPs) and aromatic protein-like substances were the main cellular components that contributed to DBP formation for both algae. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Jun 2015 · Science of The Total Environment
  • Source
    • "Natural organic matter (NOM) which occurs in water reservoirs is mainly present in two forms: (i) allochthonous NOM of terrestrial origin dominated by humic substances (HS, mostly humic and fulvic acids) and (ii) autochthonous NOM, including mainly compounds derived from algae and cyanobacteria, i.e. algal organic matter (AOM). As well as HS, AOM has received increasing attention as it can cause either aesthetic concerns (i.e., colour, taste and odour) or undesirable health effects associated with disinfection by-products (DBPs) (Lui et al., 2011; Li et al., 2012), cyanobacterial toxins (Harada, 2004) and other toxic compounds contained in NOM (Ghernaut et al., 2011). Moreover, AOM may instigate serious problems in drinking water treatment processes, especially during the decline phase of an algal bloom, when high concentrations of cellular organic matter, consisting mainly of saccharide-like and protein-like substances, are released into the source water (Zhang et al., 2010; Nicolau et al., 2015). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The study investigated the influence of cellular peptides and proteins derived from cyanobacterium Microcystis aeruginosa on the coagulation of kaolin particles during water treatment. To describe the coagulation mechanisms, coagulation system constituents (peptides/proteins, kaolin and coagulant) were characterized in terms of their surface charges. The removal mechanisms of peptides/proteins and kaolin were evaluated by the comparison of the coagulation tests performed with and without coagulant (ferric or aluminum sulfate). We confirmed the peptide/protein inhibiting effect on coagulation through the formation of dissolved complexes with coagulants at a pH value of about 6 for Fe and a pH value of about 6.8 for Al. On the other hand, we demonstrated that cyanobacterial peptides/proteins also have positive effects as they induce the coagulation of hydrophobic kaolin particles within the pH range 4-6 for Fe and 5-6.5 for Al. Interestingly, when peptides/proteins bear a sufficiently low amount of negative charge (pH < 4.5), they can coagulate with kaolin by means of electrostatic interactions even in the absence of a coagulant. The study showed that peptides/proteins produced by M. aeruginosa can serve as coagulation aids and contribute to the turbidity removal at pH values below neutral (pH < 6 for Fe and pH < 6.5 for Al).
    Full-text · Article · Oct 2013 · Separation and Purification Technology
Show more